1. Technical Field
The present invention relates to a technique for automatically sensing the feeding of individual sheets of paper in an ink jet printer, and more particularly, relates to an automatic paper sensing apparatus of an ink jet printer for automatically sensing a feeding state of successive sheets of paper.
2. Related Art
Conventional paper feeding structure in an ink jet printer is classified into two types. The first type as disclosed, for example, in U.S. Pat. No. 5,171,006 for Sheet Material Feeding Device issued to Naito, U.S. Pat. No. 5,209,591 for Sheet Guide Mechanism For A Printer issued to Mizutani et al., and U.S. Pat. No. 5,582,399 for Sheet Feeding Device Having Sheet Edge Sensor issued to Sugiura, relates to a paper cassette containing a stack of paper mounted with a slight gradient on the rear side of the main frame of the printer so that a plurality of sheets of paper stacked in the paper cassette are fed one by one toward a printer head for printing by a feed roller. The second type as disclosed, for example, in U.S. Pat. No. 5,259,607 for Automatic Paper Feeding Device issued to Hironori et al., U.S. Pat. No. 5,291,224 for Sheet Feeding Apparatus Using Pairs Of Spur Rollers issued to Asano et al., and U.S. Pat. No. 5,362,038 for Sheet Feeder For Computer Driven Printer issued to Giles et al., relates to a paper cassette containing a stack of paper mounted at the lower part of the printer so that a plurality of sheets of paper stacked in the paper cassette are fed one by one by a pick-up roller toward a printer head for printing by a feed roller.
Generally, in an ink jet printer in which the cassette is mounted upright on the rear side of a body of the printer, individual sheets of paper are fed one by one toward a printer head mounted on a carrier by a feed roller and then are printed while each sheet of paper passes through the printer head which reciprocates from side to side on a shaft. After each sheet of paper is printed by the printer head, the printed sheet of paper is fed toward a discharge tray by a discharge roller. An exemplary paper feed sensing apparatus typically includes an optical sensor and an actuator feed which determines related rotational direction of a motor after sensing the existence of the paper. When the paper is not present in the paper feeding structure, the actuator feed interrupts the optical sensor so that the paper feed sensing apparatus can sense that a paper is not present. Conversely, when the paper is present in the paper feeding structure, the optical sensor causes one end of the actuator feed to move upwardly so that the paper feed sensing apparatus can sense that the paper is present. However, if a message indicating that the paper is not present is generated during a printing operation, paper can only be subsequently printed by manually pushing a paper supply button mounted separately on the ink jet printer. If the paper supply button is not mounted on the ink jet printer, then the user must first turn off the power supply and turn the power supply back on before a printing operation can be initiated to print information on successive sheets of paper. This requirement of a paper supply button, as I have observed, is unnecessarily complicated and cost prohibitive. Accordingly, further improvement in an automatic paper sensing mechanism of an ink jet printer can be contemplated.